What is the risk of Group B Strep in pregnancy?

Group B Streptococcus (also known as GBS or group B Strep) is a bacteria that’s carried by roughly a fifth* of women in the UK, typically in their vagina and bowel.Usually, it doesn’t produce any symptoms or cause any health problems, so women don’t know they’re carrying it. It’s not a sexually transmitted infection or a sign of poor hygiene or health.

The risks of Strep b in pregnancy

Most pregnant women who carry Group B Strep, do so without any problems, but there is a small risk that if you are a carrier, GBS can pass to your baby during labour. In a majority of these cases the baby will carry GBS and remain perfectly happy and well too, but in some rare cases, babies can develop a GBS infection, which can cause complications and serious illness. While infection is usually early onset (occurring within the first week of a baby’s life), in a third of cases the infection is late onset (occurring when a baby is between 1 week and 3 months old).

In the worst cases of newborn infection, strep b bacteria can spread quickly and become life-threatening, causing septicaemia (bloodstream infection or blood poisoning), pneumonia (lung infection) and meningitis (inflammation of the fluid and linings of the brain).

Fortunately, it’s rare – only one in every 2,000 babies born in the UK and Ireland are diagnosed with a strep B infection.

Strep B test in pregnancy

In the UK, screening for group B strep is not done routinely in pregnancy, but it’s sometimes picked up by chance during tests for other conditions (usually through vaginal swabs or urine tests).

However, new guidelines from The Royal College of Obstetricians and Gynaecologists (RCOG) now recommend that women who have tested positive for GBS in a previous pregnancy have a test done in subsequent pregnancies to see if they are still carrying GBS. The test, which involves a vaginal and rectal swab, will be offered between 35 and 37 weeks of pregnancy.
If you are told you are carrying the bacteria at any point, ask your GP or midwife for more information.

Factors that increase the risk of an infection

Several things can increase the risk of group B strep passing from mother to baby and causing infection:
• if you have had a baby previously who developed the infection
• if you have a high temperature during labour
• if you go into labour before 37 weeks of pregnancy – the earlier your baby is born the greater the risk
• if your baby is born more than 18 hours after your waters break.

Protecting babies at higher risk of strep B infection

If your baby does face a higher risk of strep B, you will be offered antibiotics (intravenously) during labour to lower the risk of your baby developing an infection.

When GBS is found in a vaginal swab during pregnancy, antibiotics are usually not given straightaway as it doesn’t actually reduce the chances of infection being passed on to your baby. This is because GBS comes back comes back pretty soon after you finish your antibiotics. As bacteria are more likely to be transferred during labour, the most effective way of reducing infections in babies therefore involves having antibiotics, by injection, during labour.
Once your baby has been born, if they do face a higher risk, you will find the medical team will monitor them more closely for signs of an infection. You will be encouraged to breastfeed regardless of GBS.

Signs of an early-onset strep B infection in newborn babies

Keep an eye out for several key signs:
• being floppy and unresponsive
• not feeding well
• grunting
• high or low temperature
• fast or slow heart rates
• fast or slow breathing rates
• irritability

If you notice these signs, get immediate medical attention. If doctors are worried that your baby is showing signs of infection, they’ll arrange tests and give your baby intravenous antibiotics.
Most babies develop symptoms within 12 hours of being born so if you go home soon after having birth, or you have a home birth, keep a lookout for these warning signs.

Remember strep B infections are rare

While these infections are thankfully rare, early diagnosis and treatment is critical, so if you think your baby is developing signs of an infection, seek immediate medical attention.

The information on this website is for general information and it is not intended as, nor should it be considered as a substitute for seeing your own GP, midwife or healthcare professional. You are advised to seek professional medical advice if you have any concerns or suspect you have a medical problem.